Perforated plastic films are sometimes used in structures wherein it is necessary to control the passage of fluids (liquids or gases) and solid particulate matters. Such structures include geotextile fabrics, chemical release packages and packages designed to control the moisture content or permit the passage of oxygen or other gases, etc. Heretofore, perforated plastic films have been produced by mechanical means, such as by mechanical punches or hot needles, or by the application of laser beams. Needless to say that the application of laser beams is a rather cumbersom technique, expensive and requires great precision. Mechanical punching, on the other hand, is not entirely satisfactory and requires complicated assembly and tooling, particularly when it is desired to produce a matrix of perforations of various patterns and/or sizes.
Accordingly, it is an object of the present invention to provide a more reliable and more economical an effective method of producing perforated plastic films.
It is also an object of this invention to produce a perforated plastic film wherein the sizes and numbers of perforations are precisely controlled in accordance with a predetermined matrix.
The foregoing and other objects and features of this invention will become more evident from the ensuring detailed description and the accompanying drawings.